Single serving beverage capsules or cartridges for use in beverage preparation machines are becoming increasingly popular. Such capsules come in a variety of forms for use in the preparation of beverages that include espresso coffee, drip coffee, tea, hot chocolate, soups, etc. In one version, the capsules have a single chamber commonly defined by a plastic or aluminum body having an open top enclosed with a cover formed from a foil, plastic or other polymer. Typically, the chamber is filled with infusion ingredients, such as ground coffee, for producing beverages in a beverage machine. Hot water is injected by the beverage preparing machine into the chamber containing the infusion ingredients, causing the beverage to flow from the capsule into a user's cup or other reservoir.
In the case of single chamber beverage capsules such as those described above, the cover is commonly glued and/or heat sealed to the upper rim of the container. The cover thus seals the contents within the capsule and is pierceable to permit the beverage machine to insert a probe or other device through the cover so that water can be injected into the interior of the chamber. In order to retain the freshness and to prevent spoilage of the ingredients retained within the chamber, the seal between the cover material and the upper rim of the capsule must be of a high integrity. An inferior or incomplete seal may result in a degradation of the freshness of the ingredients, the infiltration of contaminants into the chamber and/or a potential loss of a portion of the capsule's ingredients.
During the manufacturing process for capsules of the above nature, it is thus desirable to perform at least periodic inspections in order to confirm the integrity of the seal of the lid or cover. For many applications a periodic testing and statistical analysis is sufficient. However, in other instances the particular material retained within the capsule, its inherent value, and its likelihood to suffer spoilage if exposed to the environment, may necessitate a complete testing of all capsules on an assembly line.
Others have proposed a wide variety of different methods to test for leaks in such containers, and in particular, leaks in the seal between the upper rim of the container or capsule and its cover or lid. Where the capsule contains dry goods (for example coffee, tea, hot chocolate, etc.) there will also be air or other gas present within the sealed chamber. Even where the capsule contains a liquid, there will typically be some degree of air or gas at the top of the container. In such cases a common method for leak detection is to submerge sealed capsules into a water tank and observe any bubbles emanating from the containers. Bubbles from the container will indicate the escape of gas through a breach. Although this method of water testing can be relatively simple and effective, it is slow and laborious and is impractical to conduct on a large scale or on the entire production of capsules or containers. Water testing is therefore, for the most part, restricted to a random sampling and a statistical analysis applied to the results of that random sampling. Further, while such methods will generally identify leaks, they do little to indicate the position or precise location of the leak. Since most of the capsules or containers in the nature of those described above are formed, filled and sealed on an assembly line, the location of a particular leak can be important for troubleshooting a potential problem in the manufacturing process. A leak at the same particular location on multiple capsules may indicate a problem in the sealing stage of the assembly process (for example a lack of sufficient heat at a particular location, the lack of an adequate application of adhesive, etc.).
Although a significant use for such capsules is in the beverage making industry, there are a wide variety of other applications of sealed containers for which leak testing is desirable. Many of those applications are in the food industry where products such as juices, individual fruit or dessert servings, yogurt, individual cheese packages, etc. are often stored in containers or capsules having a hermetically sealed and flexible lid or cover. Capsules or containers where a high integrity seal is often required are also used in the pharmaceutical industry, as well as a number of other industries.
Accordingly, there is constantly the need for new methods and devices to assist in the detection of leaks in hermetically sealed containers.